running new feeder from exposed-basement load center to basement wall-mounted subpanel, + adj. duplex receptacle, THEN outside for 2 deck circuits

Question

Project Context: about to place deck boards on wholly redone, raised, attached, front of house/front door accessing, 6'x20' deck. We are in IL, just south of the WI state line.

Before laying these boards, I'd like to run the electrical for receptacles. Under deck access will be available moving forward, but cramped and sloped. I'd like to also run wiring for LV landscape lighting, but that will have to wait. My wife just wants the deck done, and since I'm the one who does all of the outside maintenance, holiday decorating, etc, am the only one who sees the value of forethought vs just getting it done.

What I'd like to do is:

1. run 20A feeder 70' total (two 90deg turns) from the house's main 200A service panel (oppo corner of the rectangular basement) to just about where the outside electrical will exit the basement. Mount subpanel here.

2. have outside, two separate branch circuits: under deck receptacles (6 or 8 duplex boxes) affixed toward the deck's rim joists (these will support numerous holiday decorations and possibly extension cords for occasional powered tool works) AND receptacles that will be up and available toward the house-side of the deck, for access and use by people sitting on the deck.

3. I'd like both outdoor circuits switch controlled, for which I'd have a dual switch box mounted in the deck corner. This would allow, for example, someone to "turn off" either/both circuits as desired. Some times it's nice to sit outside and have no more than star or moon light.

Regarding the dual receptacle mounted adjacent to the indoor subpanel, that would be for plug-in of a landscape lighting transformer. I've been researching these, and feel like I'd prefer to have that transformer mounted indoors, next to the subpanel, with the only exiting considerations being the LV wiring and the thin lead for lighting photocell, which would get mounted nearby.

Reasoning is our layout doesn't make easy "hiding" the LV transformer outside, weather impacts are negated, LV controller access is as easy as walking down into the basement. Ideally, this LV circuit too would have an outside mounted switch box, into which probably three separate lighting zones could be independently switched on/off, downstream of the photocell. While the LV lighting is a separate project altogether, I bring it up simply because of my interest in powering that transformer off the same feeder circuit as supplies the deck outlets.

I understand the wet environment considerations, so that's being factored into my materials list, incl in-use, weather-resistant covers, weatherproof switch box, etc. NEMA 3R or even 4 for an outside junction box, should that be needed/recommended.

I aim to use 12/3 solid for the outdoor circuits, probably out of a Southwire 12/3 Black/White/Green Solid CU CoilPAK SIMpull THHN Tri-Wire.

I'd likely use Schedule 80 for all outdoor straight runs, with each receptacle box fed wiring via LiquidTight. All receptacles will be pigtailed, instead of series wired. I figured I'd have each outdoor circuit's first receptacle be a GFCI, providing that required coverage to each downstream receptacle.

I can draw something out and post it, if that's preferred.

I've been reading, researching and thinking about this for long enough now that I've some sort of paralysis by analysis going on, and as mentioned, a wife who has and is being pretty patient, but now that Spring has sprung, that's about to come to a swift end. She just wants back her deck. I get it; I do too.

Appreciate in advance any/every ones' time, attention and assistance.

EDIT: Point was made that the Southwire CoilPAK via H.D. shows as THHN, when THWN is required. Here's a C/P directly from Southwire's site, covering CoilPAK:

Southwire® SIMpull THHN® copper conductors as part of the SIMpull CoilPAK™ Wire Payoff are primarily used in conduit and cable trays for branch circuits in commercial or industrial applications as specified in the National Electrical Code. Voltage for all applications is 600 volts. SIMpull THHN® copper conductors are designed to be installed without application of a pulling lubricant. These conductors have multiple ratings. Depending upon the product application, allowable temperatures are as follows:

THHN or T90 Nylon- Dry locations not to exceed 90° C
THWN-2- Wet or dry locations not to exceed 90° C or locations not to exceed 75° C when exposed to oil
TWN75- Wet locations not to exceed 75° C
MTW- Wet locations or when exposed to oil at temperatures not to exceed 60° C or dry locations not to exceed 90° C (with ampacity limited to that for 75° C conductor temperature per NFPA 79)
AWM- Dry locations not to exceed 105° C only when rated and used as appliance wiring material

Answer 1

Put the GFCIs inside, too. Even "weather resistant" ones die faster outside.

If your LV needs are small enough, plug the transformer into one of those. If you need Moah Powah! just put two deadfront GFCIs inside for the two circuits going outside, before they go outside, and run the LVT off its own circuit breaker on the sub-panel.

Remember to allow for working space at the sub-panel. 30" wide, 36" out, 78" high, kept clear at all times (not useable for storage.) Sometimes that means running 2 or 3 circuits from the main (or a subpanel by the main, sharing or only slightly increasing its working space) is the better option.

Using solid wire in conduit is like slapping yourself in the face. Stranded is more flexible and easier to pull and generally costs maybe a penny more per foot at these sizes. Get quality outlets with screw-and-clamp attachments for the wires that don't make connecting stranded wires irritating, and use stranded wire.

If you do the conduit right, you don't have to get the wiring done to get the deck on and the wife happy. Just get the outside conduit done and the deck over it, then worry about the electrical after the deck is on.